Former Republican presidential candidate Ben Carson speaks after announcing he will endorse Republican presidential candidate Donald Trump during a news conference at the Mar-A-Lago Club in Palm Beach, Fla., on March 11, 2016. (Associated Press) **FILE** more >

“I haven’t made up my mind what to think,” said Robert Varney, a former Carson supporter in Alton, New Hampshire. “I’m not crazy about Trump’s fanatics, but maybe Dr. Carson can have a positive influence and get him to calm down in the next few months.”

Mr. Varney is troubled by recent violence at Trump rallies and how Mr. Trump has responded to it, by seemingly calling for his supporters to fight back against those who incite them. But Mr. Varney isn’t disappointed Mr. Carson chose to support Mr. Trump, and hopes the real estate mogul will take Mr. Carson into his counsel.

Michael Callagy, a Carson supporter in Alton, Iowa, feels much the same.

“I don’t see much similarity in Trump and Dr. Carson other than they’re both outsiders and men,” said Mr. Callagy. “I must say, I’m bewildered at the endorsement. I can’t tell you if I’m upset about it or not.”

Mr. Callagy said Mr. Carson’s endorsement won’t necessarily led to his vote for Trump in November.

“Trump just doesn’t meet my criteria for president. He doesn’t have the right moral base, I don’t think he can do the job, and he’s not a uniter or reconciler, and that’s what we’re going to need for the party,” Mr. Callagy said.

“There are two different Donald Trumps,” Mr. Carson said at the endorsement. “The one you see on the stage and the one who is very cerebral.”

“Some people have gotten the impression that Donald Trump is this person who is not malleable, who does not have the ability to listen, and to take information in and make wise decisions and that’s not true,” Mr. Carson explained.

He called for the Republican Party to unite around the front-runner and to not let party operatives decide who should be elected, saying that the will and the vote of the people should be heard. Establishment Republicans, who have initiated a “Never Trump” campaign, are pushing the idea of a contested convention, which Mr. Carson is firmly against.

“What I’ve been seeing recently is political operatives once again trying to assert themselves and trying to thwart the will of the people,” Mr. Carson said. “I find that to be an extraordinarily dangerous place right now.”

On his Facebook page, explaining his endorsement to his supporters, Mr. Carson argued the businessman, being an outsider, can buck party politics and deviate the nation from it’s current direction of “uncertainty” and “ruination.”

The posting was met with mixed response, with more than 104,347 Facebook likes. Another 10,028 were saddened by the post, and another 8,487 loved it, according to Facebook’s new reactions.

“Thank you Dr. Carson for your support for Trump!” wrote Angela Pink on Mr. Carson’s posting. “I am your loyal supporter who donated and volunteered for you in two states. I will always admire you and support you and THANK YOU for keeping us united against progressive democrats and establishment big-government republican elites. God Bless!”

Other postings weren’t so favorable.

“Dr. Carson, you have lectured us for months about civility. Now you are endorsing the most uncivil candidate in the history of elections!!,” wrote Debra Fuyan Fitch. “I am very confused about who you really are. I had so much respect for you until this primary cycle.”

Others agreed.

“Our country is in the midst of a moral crisis and you’re asking us to rally around and support someone to become the leader of this country that’s at a crossroads who at best is morally ambiguous and completely morally self-serving, self aggrandizing to the point of self exaltation with vindictive retaliatory hallmarks at worst,” David and Melissa Johnson wrote. “This makes absolutely no sense to me.”

Still some were forgiving.

“So many of you are critical of Ben for his endorsement of Trump,” wrote George Christmas. “Your rationale is one man exhibits Christian values and the other does not. So, is it not possible for the Christian to influence the other? Isn’t that what Christians are called to do?”

Teresa Brink Hutto agreed.

“Personally, if Donald Trump is elected, I can’t think of a better man to be in place to give him wise, Godly counsel. I am proud of Carson for not withdrawing from his calling to use his gifts and talents to serve the American people.”

Mr. Trump said Mr. Carson would advise him on education and health policy and will make campaign stops for him. The two haven’t spoken about any formal roles Mr. Carson will take on if Mr. Trump is elected to the White House, but Mr. Carson has said he’d be willing to consider becoming Mr. Trump’s running mate, if asked.